Injection molded article

ABSTRACT

An injection molded article has at least a first portion with a first cross sectional thickness and an integral second portion having a second cross sectional thickness. A plurality of hollow projections extend into the second portion, thereby allowing the second portion to have an overall cross sectional thickness substantially greater than the first portion thickness.

FIELD OF THE INVENTION

[0001] The present invention is related to injection molded articles. More particularly, the present invention is related to injection molded articles having portions of different thicknesses.

BACKGROUND OF THE INVENTION

[0002] Injection molded articles are known in the art. These components may be made of hardened polymers such as thermoplastic or the like. To form the component, a multi-part mold may be provided having a cavity in the shape of the component. A polymer is introduced to the mold cavity in liquid or resin form through a gate under pressure and then changes phase to a solid while in the mold. After solidification, parts of the mold may be disengaged to allow the solidified article to be removed. The polymer phase change to solid in the mold may occur through multi-reactant chemical reaction, application of heat, removal of heat, or the like.

[0003] Regardless of the particular polymer phase change method, the process generally involves substantial heat energy, with the component pliable and otherwise deformable while at elevated temperature. After solidification, the solid component remains in the mold cavity until it has cooled sufficiently. Defects related to uneven cooling or removal from the mold before complete cooling are known, and include deformation, cracking, surface blemishes, and the like.

[0004] Such temperature related defects are acute for particular types of injection molded articles. Components having a variance in cross sectional thickness, for instance, are particularly susceptible to a variety of undesirable injection molding effects related to uneven cooling. If the cross sectional thickness of a component varies by too much from section to section, wider sections of the component may suffer defects including bubble formation and so-called “sinking”. As these wider or thicker sections cool at a slower rate than the thinner sections, contraction can occur in the cooler portions and thereby exert “pulling” forces on the still pliable un-cooled sections. These and other effects can cause indented “sinks” or surface cracking. Also, the center portion as it cools may be unable to de-gas through the hardened skin, leading to interior bubble formation. As a result of these difficulties, in the prior art only limited variation of thickness of injection molded articles is practical. That is, only limited changes in thickness are possible from one component section to another.

[0005] These problems related to different thicknesses or cross sectional thicknesses have heretofore limited the ability of components to be shaped in sufficient detail for many applications. For example, many applications require irregular component cross-sections or otherwise have sections of differing thicknesses. For reasons discussed herein above and others, it has been difficult to provide injection molded articles practical for these applications. These problems are also particularly acute for components molded of transparent or translucent materials. In such components, problems occurring during the cooling process may lead to defects in the body of the component such as bubbles, cracking, or the like that would not be apparent in non-transparent or opaque components are visually detectable.

[0006] For purposes of cost efficiency and manufacturing throughput, it is desirable for injection molded articles to have relatively short required production times. In the injection molding process, component cooling time is a significant portion of the molding process. In some processes, in fact, cooling time can consume 50% or more of the molding process time. Thus shortened cooling times increase manufacturing efficiency and decrease costs. Shortened cooling times must be balanced, however, against increased defects caused by removing components before cooling to a stable temperature has occurred. Reducing the molded component wall thickness can reduce cooling time. It is known that cooling time increases in a greater than linear fashion with wall thickness. Accordingly, decreases in wall thickness have proportionally greater cooling timesavings. Component wall thickness is often needed, however, for structural stability and support.

[0007] Accordingly, there are unresolved needs in the art.

SUMMARY OF THE INVENTION

[0008] The present invention is directed to an injection molded article having a first portion with a first thickness, an integral second portion with a second thickness, and a plurality of projections extending into the second portion. A molded component of the invention is further characterized in that a ratio of the second portion thickness to the first portion thickness is at least about 1 to 0.75.

[0009] The projections allow the second portion to have a substantially greater thickness than the integral first portion while avoiding many problems of the prior art such as sinking, bubbles, cracking, and the like. The preferred projections accomplish this by providing increased surface area, and by in effect sub-dividing the thicker first portion into sections of smaller thicknesses. The injection molded article of the present invention thereby solves many of the otherwise unresolved problems of the prior art.

[0010] The above brief description sets forth some features and advantages of the present disclosure so that the detailed description that follows may be better understood, and so that the present contributions to the art may be better appreciated. There are, of course, additional features of the invention that will be described hereinafter that form the subject matter of the claims appended hereto. In this respect, before explaining preferred embodiments of the disclosure in detail, it is to be understood that the disclosure is not limited in its application to the details of the construction and the arrangements set forth in the following description or illustrated in the drawings. The present invention may be practiced in various additional ways, as will be appreciated by those skilled in the art. Also, it is to be understood that the phraseology and terminology employed herein are for description and not limitation.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]FIG. 1 is a perspective view of a first embodiment of an injection molded article of the invention;

[0012]FIG. 2 is a top plan view of the first embodiment;

[0013]FIG. 3 is a cross sectional view of the first embodiment along the line 3-3 of FIG. 2;

[0014]FIG. 4 is a perspective view of a second embodiment of an injection molded article of the invention;

[0015]FIG. 5 is a top plan view of the second embodiment;

[0016]FIG. 6 is a cross sectional view of the second embodiment along the line 6-6 of FIG. 5;

[0017]FIG. 7 is a perspective view of a third embodiment of the invention;

[0018]FIG. 8 is a partial cross sectional view of the third embodiment taken along the line 8-8 of FIG. 7.

DETAILED DESCRIPTION

[0019] Turning now to the drawings, a first embodiment of an injection molded article of the invention comprises the article 10 as shown in various views by FIGS. 1-3. The article 10 comprises a first portion 12 and a second portion 14 integral with the first portion 12. The second portion comprises a first surface 16 and a second surface 18 opposite the first surface 16. The second portion 14 further comprises a plurality of substantially cylindrical shaped projections or bores 20 extending from the first surface 16 into the second portion towards the second surface 18.

[0020] As shown by FIG. 3, the first portion 12 has a thickness of A₁, while the second portion has a varying thickness between surfaces 16 and 18 with a maximum of B₁. It will be appreciated that the term “varying thickness” as used herein is intended to refer to a condition of the first and second surfaces being separated from one another by different distances. The projections 20 preferably extend by varying distances into the second portion 14, so as to leave a substantially equal thickness between each projection 20 and the second surface 18. That is, each of the projections 20 preferably has an end 22 distal from the first surface 16 that is separated from the second surface 18 by a distance C₁ as illustrated by FIG. 5. Preferably, the distance C₁ is equal to or less than the distance A₁. Also, as illustrated in FIG. 2, the projections 20 are preferably separated from one another in the horizontal plane by a distance D₁ that is substantially equal to the distance C₁.

[0021] In the molded article 10 the second portion 14 has an overall “apparent” thickness that is much larger than the actual thickness of individual sections of the lower portion body. With reference to FIGS. 2 and 3 by way of illustration, the second portion 14 thickness B₁ is substantially greater than the distances C₁ or D₁. Put another way, although the overall “apparent” thickness is B₁, at any point in the body of second portion 14 a distance to a body surface is less than C₁.

[0022] This aspect of the present invention solves many problems of the prior art. For example, seemingly “thick” portions of injection molded articles can be achieved that are comprised of sections having much “thinner” thicknesses. Cooling times for the molded components are thereby significantly reduced to achieve time and cost savings. Also, the projections allow the component of the invention to retain substantial structural strength in the second portion. With reference to FIG. 3 by way of illustration, placement of the projections 20 allows for relatively thin wall sections, but also allows for retention of structural strength between the first surface 16 and the second surface 18 as a substantial thickness exists horizontally in the region therebetween. Substantial weight savings are likewise achieved.

[0023] An additional important advantage of the present invention is that injection molded articles can be created that have a substantial variance in overall cross sectional thickness from one portion to another. This may be illustrated through reference to FIG. 3, where it is apparent that the thickness B₁ of the second portion 14 is substantially larger than the thickness A₁ of the integral first portion 12. Through the present invention, in fact, ratios of second portion thickness B₁ to first portion thickness A₁ can be achieved in the range of about 1 to 0.75, about 2 to 1, about 3 to 1, about 4 to 1, about 6 to 1, or greater. In the thicker second portion 14, cooling occurs at substantially the same rate as in the thinner first portion 12 as the distance to the surface from any point in the body of the second portion 14 is substantially consistent with that of the first portion 12. Problems of the prior art such as sinking, cracking, warping, bubble forming and the like are thereby substantially reduced or avoided.

[0024] It will be noted with reference to FIG. 3 that the thickness of the second portion 14 varies, with the thickness B₁ representing a maximum. Also, although the embodiment 10 has shows a first portion 12 with a constant thickness A₁, other invention embodiments will comprise a varying thickness for the first portion. In calculating a ratio of the two portion thicknesses for purposes of this invention, an approximate maximum value for the second portion thickness should be compared with an approximate minimum for the first portion thickness.

[0025] It will also be noted that the precise location of a border separating the first portion 12 and the second portion 14 is not important to the present invention. Indeed, it will be appreciated that a border between the two portions could be located as desired, so long as the second portion has a plurality of projections extending into it, and so long as second portion thickness is greater than the first portion's. It is further noted that the projections may also extend into the first portion.

[0026] FIGS. 4-6 illustrate a second embodiment 40 of the invention. The general Y shape of the injection molded article 40 is illustrated in perspective in FIG. 4, in top plan view in FIG. 5, and in cross section in FIG. 6. The article 40 comprises a lower first portion 42 and an upper second portion 44. The second portion has a first surface 46 and an opposite second surface 48. A plurality of projections in the shape of channels 50 is comprised in the second portion 44 extending from the first surface 46 towards the second surface 48. Each of the channels 50 has an end 52 distal from the first surface.

[0027] It is noted with reference to the articles 10 and 40 by comparison that many projections are possible with practice of the invention in addition to the channels 50 and the bores 20 illustrated. For example, continuous projections may include channels and grids; discrete projections may be made in a variety of shapes, including, ovals, squares, diamonds, triangles, or other geometric shapes; irregularly shaped projections may also be used. Further, it is noted that invention embodiments are not limited to comprising only projections extending from the first surface towards the second surface, but could for example comprise additional projections extending from the second surface towards the first, or could comprise projections extending into any other surface. Those knowledgeable in the art will likewise appreciate that the present invention is not limited to any particular number of projections, but instead may be practiced with any number that may be practical or otherwise desirable.

[0028] As best illustrated by FIG. 6, the projections 50 of the article 40 allow the second portion 44 of significantly greater thickness B₂ than the thickness A₂ of the first portion 42. FIG. 6 also shows a distance C₂ separating the distal end 52 of each of the channels 50 from the second surface 48. FIG. 5 shows the distance D₂ that separates each of the channels from one another. Preferably, the distances C₂ and D₂ are substantially equal, and are substantially equal to or less than the distance A₂. Alternatively, when considering an injection molded article such as the article 40 having a first portion 42 with a varying thickness, the distances C₂ and D₂ may be set as equal to or less than the average thickness A₂′ of the first portion 42 as opposed to the minimum thickness A₂. Maintaining these preferred relationships helps to ensure equal cooling of the various portions of the article 40 as the maximum distance from the interior of any portion to an article surface is kept substantially consistent.

[0029]FIG. 7 is a perspective view of a third embodiment of the invention. In particular, FIG. 7 shows an injection molded article comprising a footwear component 100 which may be useful, for example, for creating a structural cradle for holding the heel portion of a foot in a shoe. The component 100 comprises a lateral side 102, a rear side 104, and a medial side 106. Each of these sides 102-106 rises substantially vertically. As used herein the term “substantially vertical” is intended to broadly refer to a direction having a substantial vertical component, and is not intended to be limited to any particular degree of upward orientation. The component 100 is further characterized by an interior first surface 108 and an exterior second surface 110.

[0030] Each side 102-106 comprises a first portion 112 and a second portion 114. As best illustrated in the cross section view of FIG. 8, the second portion 114 has a varying thickness defined between the interior surface 108 and the exterior surface 110. A maximum value for this thickness is represented in FIG. 8 as B₃. The injection molded footwear component embodiment 100 further comprises a plurality of projections in the form of channels 116 extending into the second portion from the first surface 108 towards the exterior second surface 110.

[0031]FIG. 8 illustrates the top portion 112 having a thickness A₃ that is substantially smaller than the lower portion cross section thickness B₃. A lower portion thickness B₃ can be achieved that is greater than the top portion thickness A₃ by values of 5 mm or greater. For example, the top portion 112 thickness A₃ can be less than or equal to about 3 mm, and the bottom portion 114 thickness B₃ is greater than or equal to about 7 mm.

[0032] It will be noted that in the component 100 the thicknesses of the first portion 112 and second portion 114 vary. As noted above, in calculating a ratio of the two thicknesses for purposes of this invention, an approximate maximum value for the lower portion thickness should be compared with an approximate minimum for the top portion thickness. It will also be noted that if an edge such as the top edge 120 exists where the first and opposite second surfaces converge, the thickness of the first portion 112 can go to zero. That is, the thickness of the top portion 112 approaches zero as the tip is neared. Under such circumstances, in order to obtain a meaningful thickness measurement for purposes of the present invention measurement of the thickness is taken only after an “edge zone” has been passed.

[0033] With reference made to FIG. 8, the edge zone is illustrated as element 122 having a length E. Preferably, the length E is about equal to or greater than the distance C₃. That is, the top portion cross sectional thickness for purposes of this invention should be determined at a distance of at least C₃ from the edge, where C₃ is substantially equal to the distance separating the hollow projection distal ends 118 from the exterior second wall 110. For the example footwear component 100 of the invention, an edge zone of at least about 1 mm is preferred.

[0034] The channels 116 preferably extend by varying distances into the lower portion 114, so that a substantially equal distance or thickness C₃ separates each channel distal end 118 from the exterior second surface 108. Also, the channels 116 are separated from one another vertically by a distance D₃ that is preferably substantially equal to the distance C₃.

[0035] This preferred configuration results in the lower second portion 114 having an overall cross sectional thickness that is much larger than the actual thicknesses of the individual sections of the lower portion body. With reference to FIG. 8 once again by way of illustration, the lower second portion 114 overall thickness B₃ is substantially greater than the distance C₃. Put another way, although the overall cross sectional thickness is B₃, at any point in the body of the lower portion 114 a distance to the body surface is about half of the distance C₃.

[0036] The article 100 may be comprised of a translucent or transparent material so that the channels 116 are visible through the exterior second surface 110 for providing a desirable aesthetic effect. An example material of construction for achieving transparency comprises urethane polymer. Indeed, it will be appreciated that injection molded articles of the invention may have an aesthetic appeal separate from their utility. By way of example, it has been found that selection of one particular type of projection over a different type, the arrangement of the projections, the “clearness” and/or the coloring of the materials of construction, the article shape and size, and the like may result in a unique non-functional appearance of an article of the invention. Reference is made to the commonly owned and co-pending U.S. Design patent application Ser. No. 29/146,676 showing a footwear component having a particular combination of non-functional design elements.

[0037] Those knowledgeable in the art will appreciate that injection molded articles of the invention may be made using generally known injection molding techniques. Referring to the footwear component 100 by way of example, projections 116 are formed by mold inserts. The inserts for the projections, if made from materials such as metal, may be useful to control the cooling of the component. As will be appreciated by those skilled in the molding arts, such molds will be comprised of multiple inserts of other parts, some of which may be required to be movable so that the molded component can be removed from the mold.

[0038] The advantages of the disclosed invention are thus attained in an economical, practical, and facile manner. While a preferred embodiment has been shown and described, it is to be understood that various further modifications and additional embodiments will be apparent to those skilled in the art. It is intended that the specific embodiments herein disclosed are illustrative of the preferred and best modes for practicing the invention, and should not be interpreted as limitations on the scope of the invention as defined by the appended claims. 

What is claimed is:
 1. An injection molded article comprising: a first portion having a first thickness; a second portion integral with said first portion and having a second thickness, said second portion further comprising at least a first surface and a plurality of projections extending into said second portion from said first surface; wherein a ratio of said second portion thickness to said first portion thickness is at least about 1 to 0.75.
 2. An injection molded article as in claim 1 wherein said ratio of said second thickness to said first thickness is at least about 1 to 0.5.
 3. An injection molded article as in claim 1 wherein said ratio of said second thickness to said first thickness is at least about 1 to 0.25.
 4. An injection molded article as in claim 1 wherein said ratio of said second thickness to said first thickness is at least about 6 to
 1. 5. An injection molded article as in claim 1 wherein said second thickness is at least about 5 mm greater than said first thickness.
 6. An injection molded article as in claim 1 wherein said projections comprise channels.
 7. An injection molded article as in claim 1 wherein said second portion has a second surface opposite said first surface, wherein said second portion thickness between said first and second surfaces varies, and wherein each of said plurality of projections has a distal end a substantially equal distance from said second surface.
 8. An injection molded article as in claim 7 wherein said projections are separated from one another by a substantially equal distance.
 9. An injection molded article as in claim 8 wherein said distance separating said projections from one another is substantially equal to said distance separating said distal ends from said second surface.
 10. An injection molded thermoplastic component comprising: a first portion having a first thickness; a second portion integral with said first portion, said second portion having a first and a second surface and a varying thickness defined between said first and second surfaces, said thickness having a maximum; a plurality of projections extending into said second portion from said first surface, each of said projections having a distal end terminating at a substantially equal distance from said second surface, said projections separated from one another by a substantially equal distance; and wherein said maximum thickness of said second portion is at least about twice as large as said first portion thickness.
 11. An injection molded footwear component comprising: a substantially vertical interior surface and a substantially vertical exterior surface; an upper portion and a lower portion defined between said interior and exterior surfaces, said upper portion having a minimum thickness, said lower portion having a varying thickness; a plurality of projections in said lower portion extending from said interior surface towards said exterior surface, said projections extending from said interior surface by varying distances whereby each of said projections has a distal end separated from said exterior surface by a substantially equal distance; and wherein a ratio of said lower portion thickness at its maximum value to said upper portion minimum thickness is at least about 2 to
 1. 12. An injection molded component as in claim 11 wherein said projections comprise channels.
 13. An injection molded component as in claim 12 wherein said channels are separated from one another by a substantially equal distance.
 14. An injection molded component as in claim 13 wherein said distance separating said channels from one another is substantially equal to said distance separating said channel distal end from said exterior surface.
 15. An injection molded component as in claim 14 wherein said upper portion thickness goes to zero at a top edge of said upper portion where said interior and exterior surfaces converge, and wherein said upper portion minimum thickness is measured below an edge zone of said upper portion, said edge zone having a length substantially equal to said distance separating said channel distal ends from said exterior surface.
 16. An injection molded component as in claim 11 wherein said ratio of said lower portion maximum thickness to said upper portion minimum thickness is at least about 4 to
 1. 17. An injection molded component as in claim 11 wherein said lower portion thickness at its maximum value is at least about 5 mm greater than said upper portion minimum thickness.
 18. An injection molded component as in claim 11 wherein said upper portion thickness is less than or equal to about 3 mm, and said lower portion thickness is greater than or equal to about 7 mm. 